(117g) Role of Functional Ligands in Graphene Oxide/MoSe2 Heterostructure(HS): Effects on Doping, Excitons and Transport

An accurate control on doping of transition metal dichalcogenide system opens up new horizons of pertinence towards device application. It is observed that doping profile of the MoSe₂ can be subtly modulated upon attachment with graphene oxide (GO). In the present study, we have demonstrated a precise control on the doping by manipulating interlayer coupling, using several first principles techniques. The key findings of our investigations are enlisted as follows. 1) By using DFT calculations incorporating spin-orbit coupling, it is shown that the doping of MoSe₂ can be tuned from n-type to p-type by varying the types and concentrations of the ligands attached to the GO-layer. Analysis of the band-structure of the heterostructure implies that the gross band behaviour of MoSe₂ remains unchanged in the HS. Attachment of GO only changes the effective mass of the carriers in the GO-bands appearing at the midgap and thus controls the transport properties. The optical properties of the HS are fully controlled by MoSe₂; 2) Investigation of the noncollinear behavior of magnetic property indicates that with the increment of ligand concentration, the almost isotropic magnetic moments of the heterostructure (HS) increases in all three directions; 3) Comparison of static optical property corresponding to the partial density of state reveals that the optical bandgap of pristine MoSe₂ is ~1.5 eV due to direct interband transition from valance to conduction band. Upon formation of HS with GO, many midgap states have been generated due to mutual charge transfer induced buckling of the GO and MoSe₂ layer; 4) Investigation of excitonic properties by using time dependent DFT indicates that the optical property of MoSe₂ undergoes exciton quenching upon attachment of GO. We have also experienced band-gap renormalization behaviour for low-energy exciton peaks; 5) The transport properties of the HS undergoes substantial changes depending upon the nature of placement of metal contacts. Analysis of the device potential of the HS as channel material with lateral and vertical metal (Au) contacts is done with self-consistent quantum transport calculations, which reveals that vertical contacts are more capable of retaining the obtained doping pattern than the lateral ones. This observation can be very useful for future optoelectronic and nanoelectronic device applications of this system as phototransistors or photodetectors.